LEGO, eat your heart out. Blocks of DNA have been programmed to automatically build themselves into nanoscopic structures. Eventually the DNA programmes will be sophisticated enough to churn out minuscule therapeutic devices that work inside the body. Single-stranded DNA has already proved itself to be a useful addition to the nanotechnologist's toolbox. A very long strand can be intricately folded into complex 3D structures through a process known, appropriately, as DNA origami. These structures could be used to ferry drugs to specific sites in the human body.